The present invention relates to a hydraulic directional valve for controlling a double-acting motor with a three-way flow-regulating valve.
Such hydraulic directional valves are known, for example, from U.S. Pat. No. 3,901,264. It is used for controlling in an open circuit a neutral circulating passage which has three chambers and arranged in a housing centrally between the motor chambers and the return chambers. A three-way flow-regulating valve is arranged in the same transverse plane in which the circulating chambers are provided and extends normal to the control slider. An adjusting device associated with the three-way flow-regulating valve extends at the upper side of the valve housing between both motor ports. The disadvantage of this directional valve is that the adjusting device through its length between the pipes extending through the motor ports is poorly accessible. In addition, the upwardly extending adjusting device frequently leads to mounting problems in directional valves. The mutually normal position of the control slider and the flow-regulating valve leads to the fact that the slider openings must be worked in two normally extending axes which is expensive. Furthermore, the normal arrangement leads to a relatively complicated and therefore expensive construction of the flow-regulating valve in which also narrow cross section can take place. The arrangement of the flow-regulating valve has a further disadvantage in that it is poorly suitable for arrangement of auxiliary valves in the region of the motor port. Also, in the known construction, only an equal constant stream can be supplied to the motor ports. In addition, this directional valve has the disadvantage that the constant stream of the flow regulator can be controlled only through the associated directional valve and cannot be available for a block of several directional valves.
U.S. Pat. No. 3,415,265 discloses a hydraulic directional valve in which two motor ports are supplied with a constant stream by three-way flow-regulating valve. In this directional valve the chambers for supply, motor and return are arranged symmetrically to a neutral circulation passage having three chambers, so that the directional valve can be used for a so-called left and right arrangement. The disadvantage of this directional valve is, however, that both flow-regulating valves are arranged in the hollow control slider and therefore are not adjustable from outside. The excessive residual stream of a flow regulator is in addition supplied into the return passage. This directional valve is also not changeable in a simple manner, so that the constant stream of the flow-regulating valve is available for a block of several directional valves.